In 15 patients suffering from idiopathic faecal incontinence and in 15 matched controls, manometric studies of anorectal pressure and studies of the rectoanal reflex and rectal sensitivity were carried out. Patients with idiopathic faecal incontinence had normal resting pressure but reduced squeeze and stress pressures; the anal sphincter relaxed before a sensation of rectal distension occurred. The conclusion is that both reduced voluntary muscle contraction and impairment of rectal sensation are conducive to soiling in idiopathic faecal incontinence.